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Allergies in Cats

What is an allergy?

An allergy occurs when the immune system overreacts to an everyday substance, seeing it as potentially dangerous. The body tries to rid itself of this substance, known as an allergen, by releasing histamine causing the area affected to become hot swollen and itchy.  Allergens can cause a reaction when inhaled, swallowed or by coming into contact with the skin.  Reactions can vary in severity.

What are the symptoms of an allergy in cats?

An allergic reaction can look similar to other illnesses.  Itching is the most obvious symptom due to the release of histamine and its effect on the affected area.  Often scratching will cause damage to the skin which can then become infected causing the area to itch more, resulting in hair loss and scabs on the skin. General symptoms to look out for are: –

  • Sneezing
  • Increased scratching
  • Red, itchy skin
  • Itchy, runny eyes
  • Itchy ears and ear infections
  • Face rubbing
  • Paw chewing
  • Constant licking
  • Snoring
  • Vomiting
  • Diarrhoea
  • Behavioural changes due to constant discomfort

What causes an allergic reaction in cats?

Common allergens are:-

  • Food ingredients (most commonly beef, dairy and fish, then lamb, wheat, chicken and corn)
  • Pollens (tree, grass, weed, mould and dust)
  • Cleaning products
  • Plastics
  • Prescription drugs
  • Flea control products and insecticidal shampoo
  • Cigarette and cigar smoke
  • Perfumes

What puts a cat at risk of an allergic reaction?

All cats can develop allergies at any time of life. Atopy is the inherited tendency to be allergic. An atopic pet is inclined to have allergic reactions to air-borne materials such as dust mites, pollen and mould spores.


Constant scratching and chewing itself is probably the clearest sign your cat is suffering with an allergy, however, it is more difficult to diagnose a definitive cause.  Your vet will give your cat a thorough examination and ask you for a detailed history of your pet’s health and symptoms, including when symptoms started.  If you are able to say whether the symptoms are constant, sporadic or increase at particular times, this will help the vet with his/her diagnosis and discovering the cause.

Flea bite allergies are very common and fairly easy to diagnose due to the presence of flea bites and the fleas themselves.

If your pet is affected by pollen, his symptoms will be seasonal and only show up when exposed to those allergens.

Where the allergic reaction occurs sporadically it is unlikely to be caused by a seasonal allergen.

If your vet suspects a food allergy, your cat is likely to be placed on a prescription diet exclusively for 12 weeks.  This diet will be free of any allergy causing ingredients.  Once all allergy symptoms have gone, old foods can be reintroduced, one ingredient at a time, to see which ones might be causing the allergic reaction.

Contact allergies are most noticeable on areas not protected by fur, such as the paws and nose.  These are commonly caused by household cleaning products, shampoos, fertilizers, insecticides, natural and synthetic fibres, pollen and grasses.

Inhalant allergies are commonly caused by cigarette and cigar smoke, fireplace smoke, pollen and environmental pollutants.

Your vet may advise allergy testing if an allergic reaction lasts for a while or occurs randomly, with no obvious trigger.

What treatments are there for cat allergies?

Prevention is the best treatment for most allergies. If your pet suffers with a dust allergy, clean their bedding once a week with perfume-free detergent, and vacuum and dust twice a week. If she uses a litter tray, use dust-free unscented litter. Also, if your pet suffers with allergic reactions to other environmental allergens such as pollen and mould spores, a weekly bath may help relieve itching.  Seek advice from you vet as to the most appropriate prescription shampoo to use.

With regards to food allergies, as previously mentioned, your vet is likely to place your cat on a prescription diet, free of any allergy causing ingredients, for up to 12 weeks.  Once all allergy symptoms have gone, old foods can be reintroduced, one ingredient at a time, to see which ones -might be causing the allergic reaction. Once the allergy has been determined you vet can advise you on a specific diet suitable for your pet.

Medications are available to ease symptoms and help control allergic reactions to allergens that cannot be removed from your cat’s environment. Topical treatments such as shampoos, creams and gels can be used to sooth irritated skin.

Your vet may prescribe cortisone or steroids to help control the allergy but may also recommend allergy injections, which should help your cat develop a resistance to the allergen.

Antihistamines and fatty acid supplements can help is some cases. If your cat has a flea allergy, start a flea control program with advice from your vet as to the best product for your cat.

How to prevent allergies

Once you become aware of an allergy, do what you can to help your pet avoid the allergen. Ensure flea treatments are kept up to date. If a food allergy is detected, make sure the diet is kept to and no treats given unless checked for ingredients your pet may be allergic to.

Cats should not be exposed to cigarette or cigar smoke, especially if they have asthma.